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Split system sizesStart with the room, not the number on the box.
Split systems are sized by capacity in kilowatts, for example 3.5 kW. Smaller sizes suit single rooms and bigger ones suit living areas, but the published room guides don't agree exactly. Find the size closest to your room below, or start with the size calculator.
What size split for what size room?
| Rinnai's buyers guide | CHOICE table (via Solar Victoria) | |
|---|---|---|
| Up to 20 square metres | 2.5 kW | 2 to 2.5 kW |
| 20 to 40 square metres | 3.5 kW | 2.5 to 5 kW |
| 40 to 60 square metres | 5.0 to 6.0 kW | 4 to 6 kW |
| 60 to 80 square metres | 7.0 to 9.0 kW (its top band starts at 60) | 5 to 7 kW |
| Over 80 square metres | No separate band | 6 to 9 kW |
Why the two guides don't match
Both are rough, and both say so. Solar Victoria, which reproduces the CHOICE table, says the supplier's assessment of your home should be followed. Rinnai says higher ceilings ask more of a system, good insulation holds the temperature, and a sun-facing room can need more cooling.
Mitsubishi Electric calls a professional heat load calculation essential: one that accounts for your climate, which way the house faces, insulation, windows and doors, building materials and ceiling height.
Not sure which page is yours?
Run your measurements through the size calculator for a rough figure, then read the page for the nearest size below. The sizing guide explains the method in more depth.
If one space seems to need 8 kW or more, read the bigger sizes before you buy. At that point a multi-split or a ducted system may suit the house better than one large wall unit.
What we'd do
Where we'd start
Measure the room, including any open area it flows into, and note the ceiling height and the sunniest window. Read the page for the nearest size, then have a split specialist confirm it with a heat load before you pick a model. If the table puts your room between two sizes, that check matters most.
Split system sizes
- 2.5 kW split systems (and 2 kW)What a 2 or 2.5 kW split suits, and how to keep a bedroom unit quiet.
- 3.5 kW split systemsWhere a 3.5 kW split fits, and how to compare two units of the same size.
- 5 and 6 kW split systemsWhen a 5 or 6 kW split suits a living area, and how to measure an open-plan room.
- 7 and 7.1 kW split systemsWhat a 7 or 7.1 kW split suits, and when two smaller units beat one big one.
- 8 kW split systemsWhat an 8 kW split suits, and when the whole house needs a different system.
- 9 and 10 kW split systemsWhy 9 and 10 kW splits sit at the edge of the guides, and what to ask first.
Questions people ask
What does the kW number on a split system mean?
Is a bigger split always better?
Read next
- 01Air conditioner size calculatorA rough kW size from your room's measurements, and what that number leaves out.
- 02What size air conditioner do I need?Rough kW sizes by room, what changes them, and how an installer should check the number.
- 03Split systems explainedWhat a split is, how it heats and cools, and the rooms and homes it suits.
- 04Split system installationWhen a split suits your home, how to size it, and what a good install includes.
- 05How to choose a split systemSize, energy stars, noise, inverter and warranty conditions: what to check before you choose.
- 06Multi-split systemsOne outdoor unit, several rooms: when a multi-split fits, and the trade-offs to know.
Where this information comes from
- Rinnai Australia Buyers guide: air conditioning, 28 October 2026
- Solar Victoria (Victorian Government) Home heating and cooling upgrades buyers guide (print all), 14 July 2021
- Rinnai Australia Ultimate split system air conditioner size guide, 28 October 2026
- Mitsubishi Electric Australia Air Conditioner Buying Guide, 28 October 2026
We don't publish prices. Every home is different, so an installer's written quote is the only real number. How we write and check these pages.